Biofuel is generally a fuel derived from biomass, i.e., recently living organisms or their metabolic byproducts, such as manure from animals. Biofuel is desirable because it is a renewable energy source, unlike other natural resources such as petroleum, coal and nuclear fuels. Biofuel includes, inter alia, biologically produced alcohols, alkenes and derivatives thereof. Generally, such biologically produced biofuel can be formed by the action of microbes and enzymes through fermentation of biomass. For example, methanol can be produced from fermentation of wood or other organic materials or formed naturally in the anaerobic metabolism of many varieties of bacteria. Similarly, ethanol can be mass-produced by fermentation of starch or sugar which can be found in a wide variety of crops such as sugar cane, sugar beet and corn. Furthermore, various isoprenoid compounds can be prepared biologically from simple sugars using a host cell that has been modified to produce the desired isoprenoid compounds.
Recently, because of concerns over global warming, rising oil prices as well as decreasing oil reserves and increasing political instability in oil producing countries around the world, there are renewed interests from governments, industries and academics in biofuels, particularly biologically produced alcohols for automobiles. However, alcohols such as methanol, ethanol and propanol are volatile enough that they can cause engine vapor lock and evaporative emission problems. Furthermore, alcohols generally have a high affinity to water and therefore, they generally contain an undesirable amount of water that can cause corrosive problem to internal combustion engines that use them as fuels. As a result, there is a need for biofuels, such as non-alcoholic biofuels, that have a low affinity toward water. Further, there is also a need for biofuels that can be made reliably and reproducibly for use in internal combustion engines such as gasoline engines.